A panel held by the World Health Organization (WHO) has called for a Phase III trial of the Zaire Ebolavirus vaccine Ervebo to be investigated against the current Bundibugyo strain.
In a WHO Technical Advisory Group on candidate vaccine prioritisation (TAG-CVP) meeting, held on 31 July, with one exception, members were unanimously of the view that Ervebo should be prioritised for inclusion in a Phase III trial against the strain which is causing the current outbreak.
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There are no vaccines available against the Bundibugyo strain, and experts therefore concluded that considering the wealth of reactogenicity and immunogenicity data and population-wide safety data available for Ervebo, it could enter a Phase III trial without an initial Phase II evaluation.
They did add, however, that this study should not preclude the later inclusion of a Bundibugyo vaccine candidate, should one become available and be considered by the TAG-CVP to be suitable for evaluation in the current outbreak.
The WHO panel came to this decision based on a number of research papers and preclinical studies of Ervebo. They did note certain limitations with the research, though, including that some was not peer-reviewed, and that research-grade rVSV-EBOV material was used, rather than licensed Ervebo product in certain studies.
Despite this, all four studies showed a low level of cross-reacting binding antibodies to Bundibugyo induced by Ervebo.
Another benefit of Ervebo, which the panel unanimously agreed, is that there were no safety concerns regarding its use in a clinical research study, as the vaccine is already approved by regulatory agencies globally and has been given to hundreds of thousands of people in Africa. The WHO also has a stockpile of the vaccine, meaning a rollout would be easier.
They caveated all of this, however, adding that expectations over the potential efficacy need to be managed about its likely protective effect if used in a Phase III ring vaccination trial, as efficacy against symptomatic disease and transmission may not be high, whereas protection against a fatal outcome may be achieved.
Earlier in August, Moderna initiated a Phase I trial of its mRNA Ebola vaccine for the Bundibugyo variant. The first-in-human Phase I trial (NCT07737717), which will test Moderna’s vaccine candidate, mRNA-1469, has been approved by Health Canada. The study will take place at three sites in Canada and evaluate the safety, tolerability and immunogenicity of the mRNA vaccine in healthy adult participants. The study is expected to enrol approximately 80 participants.
The WHO has also initiated a study to investigate treatments for those infected with the virus. Through a clinical trial, dubbed PARTNERS, WHO and its international partners will evaluate the potential of two antiviral therapies alone or in combination for treating BVD. These include the first approved antiviral for Covid-19, Gilead Sciences’ Velkury (remdesivir), and Mapp Biopharmaceutical’s investigational double antibody-based Ebola therapy, MBP134 – with efforts beginning in the Democratic Republic of Congo (DRC).
Bundibugyo is one of the viruses that can cause Ebola disease and has been responsible for the active outbreak in the DRC. Although vaccines are available against Zaire ebolavirus, no vaccine is currently approved to protect against disease caused by Bundibugyo.
The current outbreak was declared a Public Health Emergency of International Concern (PHEIC) and a Public Health Emergency of Continental Security (PHECS) by the WHO and Africa Centres for Disease Control and Prevention (Africa CDC), respectively. It has already caused more than 3,000 confirmed cases and more than 1,400 deaths, making it one of the largest filovirus outbreaks in history.
